Strong Philopatry, Isolation by Distance, and Local Habitat Have Promoted Genetic Structure in Heermann’s Gull

Round 1

Reviewer 1 Report

The authors handled previous comments very well and I have no further remarks except for the following:

Line 50: Consider changing “seabirds” in “birds”. It is now a little bit a sudden switch from a general phenomena in birds to seabirds in particular.

Author Response

RESPONSE TO REVIEWER 1

We thank Reviewer 1 for agreeing to review the manuscript again and we are pleased to hear that the changes we made have addressed previous comments and suggestions.

We have changed “colonial seabirds” for “birds” in the line 50 (now in the line 44). Now, the sentence can be read like this: “Nonetheless, not all the birds are philopatric and, by extension, not all show reduced gene flow, as this phenomenon can vary significantly per species and even within species”.

We are grateful for your review; the proposed changes have allowed us to significantly improve our manuscript.

Reviewer 2 Report

You have made a lot of changes and addressed most of my points.  I still have a few questions about Fig 4 in the revised manuscript.

For the BAPS plots, it still isn’t clear what is causing the patterns.  I understand how the program works, but if there are two genetically distinct groups that are geographically distinct, you should not see birds with extremely high ancestry coefficients to the other group.  If Isabel is genetically distinct as suggested by mtDNA and msats, you’d expect all of the birds from that group to be green (in fig 4 of the revised ms) and birds from Rasa and Cardonosa to be mostly red.  The pairwise PhiST estimates also suggest that as Cardonosa (yellow) are similar to Rasa (red).  Right now the figure shows multiple birds from Cardonosa and Rasa are green (ie originate from Isabel) and 3 birds from Isabel are red.  With that level of mixing on the breeding grounds, you’d be unlikely to see two genetically distinct groups.  The 3 birds in red from Isabel, are these the same ones with H1 mtDNA?

Author Response

RESPONSE TO REVIEWER 2

We thank Reviewer 2 for agreeing to review the manuscript again and are pleased to know that the changes made have clarified most of their previous comments and suggestions.

For the BAPS analysis of Figure 4, the observed pattern is explained as follows: the mixed clustering graph is a colored partition of the grouped units (it was carried out without specifying the sampling populations to geography, that is, without restriction on the geographic origin of each of the 296 individuals included in the analysis). Each gull can be recognized by the labeling of the input file that was given to the program (the names appear in the same order as in the data), in this way we can identify the origin of everyone in the resulting graphic. Each 'sampling unit' or clustered individual is represented by a vertical bar with the color assigned according to the cluster in which it was placed. The population admixture analysis was started by testing all possible populations K = 2 to 20. Regardless of the K populations tested, the best partition always pointed to two groups and the same individuals assigned to each group. Neither population of the same species is completely isolated (PhiST = 1 rarely occurs in nature), so the observed pattern can be explained by some level of migration between the two groups found, either recent or long ago. In figure 4a, on Rasa Island, only 6 out of 266 individuals that could belong to another genetic group were observed, that is, 2.25% of the total individuals sampled on this island putatively come from another genetic group (in this case, the green cluster) and all the individuals from Cardonosa (n= 20) belong to the same red group. On the other hand, 3 out of 10 individuals sampled on Isabel Island putatively belong to the red group and have the mitochondrial H1 occurring on the other two islands (accession numbers provided by GenBank for all individuals assigned to each haplotype are shown in the supplementary material).

We appreciate your review; the proposed changes have allowed us to significantly improve our manuscript.

Reviewer 3 Report

Abstract is well written and content provides a good insight into what the manuscript. However, it exceeds the maximum number of words. Please reduce.

Keywords. Please use keywords that are not already in use in the title. Search engines look for this already, hence you lose a chance to be found, thus, cited.

Introduction is appropriate. I really enjoyed reading it as its organization is quite balanced. Objectives are clear and straightforward.

It has been long time since I have been able to revise such a complex but complete and well executed study. New information helps to understand the rationale of what was performed.

Even if the objectives of the paper are challenging, the authors managed to present the information with such a level of detail that ensures readers can use the information or even think of replicating this research in other species.

Discussion is so well conducted that it leads to solid conclusions that perfectly close a huge work.

Congratulations. I feel the work of the authors at this round of revision was definitely well directed.  I honestly feel this is worth being published.

Author Response

RESPONSE TO REVIEWER 3

We thank Reviewer 3 for agreeing to review the manuscript again and for their kind comments. Suggested changes are listed below.

We carefully reduced the abstract to less than 200 words.

Keywords other than the title are now used.

We are grateful for your review; the proposed changes have allowed us to significantly improve our manuscript.